The vasoactive intestinal peptide (VIP) stimulates prolactin release and adenylate cyclase (a.c.) activity in anterior pituitary. Since dopamine (DA) inhibits prolactin secretion by acting on D2 receptors, we investigated whether it changed the VIP activation of pituitary a.c. DA failed to affect basal a.c. activity at a concentration as high as 10-4M, but inhibited the a.c. activation elicited by VIP. The inhibition was dose-dependent and reached a maximum 50-60% reduction of the cAMP formation stimulated by 10-7M VIP) at a concentration of 10-5M d-Butaclamol (1 MuM) but not 1-butaclamol, completely blocked the dopamine inhibition while neither drug affected the a.c. activation by VIP. Apomorphine, a dopaminergic agonist, mimicked the effect of DA, whereas 1-phenylepherine and l-isoproterenol were ineffective at concentrations up to 10-5M. The results suggest that activation of D2 receptors of anterior pituitary can curtail the a.c. activation elicited by VIP. The pharmacological specificity of this D2 response is currently under investigation.